Pore partition in two-dimensional covalent organic frameworks

Covalent organic frameworks (COFs) have emerged as a kind of crystalline polymeric materials with high compositional and geometric tunability. Most COFs are currently designed and synthesized as mesoporous (2–50 nm) and microporous (1–2 nm) materials, while the development of ultramicroporous (<1 nm) COFs remains a daunting challenge. Here, we develop a pore partition strategy into COF chemistry, which allows for the segmentation of a mesopore into multiple uniform ultramicroporous domains. The pore partition is implemented by inserting an additional rigid building block with suitable symmetries and dimensions into a prebuilt parent framework, leading to the partitioning of one mesopore into six ultramicropores. The resulting framework features a wedge-shaped pore with a diameter down to 6.5 Å, which constitutes the smallest pore among COFs. The wedgy and ultramicroporous one-dimensional channels enable the COF to be highly efficient for the separation of five hexane isomers based on the sieving effect. The obtained average research octane number (RON) values of those isomer blends reach up to 99, which is among the highest records for zeolites and other porous materials. Therefore, this strategy constitutes an important step in the pore functional exploitation of COFs to implement pre-designed compositions, components, and functions.


Materials and Methods
1 H NMR spectra were measured on Bruker AVANCE III 400 NMR spectrometer, where chemical shifts (δ in ppm) were determined with a residual proton of the solvent as standard. Matrixassisted laser desorption ionization time-of-flight mass (MALDI-TOF MS) spectra were recorded on an Applied Biosystems BioSpectrometry model Voyager-DE-STR spectrometer in reflector or linear mode. ICP-MS was performed on a Perkin-Elmer Elan DRC II quadrupole inductively coupled plasma mass spectrometer analyzer. Fourier transform infrared (FT-IR) spectra were recorded on a Nicolet 6700 infrared spectrometer. X-ray diffraction (XRD) data were recorded on a PANalytical X'Pert PRO diffractometer by depositing powder on glass substrate, from 2θ = 1.5° up to 40° with 0.02° increment. Elemental analysis was performed on a Euro Vector EA3000 elemental analyzer.
TGA measurements were performed on a Mettler-Toledo model TGA/SDTA851e under N2, by heating to 800 °C at a rate of 10 °C min -1 .
Scanning electron microscope (SEM) images were collected using a Hitachi S-4800 system.
Transmission electron microscope (TEM) images were obtained with a JEM-2100F, JEOL system. Solid state nuclear magnetic resonance 13 C cross polarization magic angle spinning nuclear magnetic resonance spectra ( 13 C CP MAS NMR) were recorded on a JEOL JNM ECA600 MHz, 3.2 mm rotor, MAS of 20 kHz, recycle delay of 1 sec. Nitrogen sorption isotherms were measured at 77 K with a Micromeritics Instrument Corporation model 3Flex surface characterization analyzer. Before measurement, the samples were degassed in vacuum at 100 °C for more than 10 h. Brunauer-Emmett-Teller (BET) method was utilized to calculate the specific surface areas. By using the non-local density functional theory (NLDFT) model, the pore volume was derived from the sorption curve.

S4
Synthesis of octanoylamino-4-ethynylbenzene. In a 100 mL round bottom flask equipped with a magnetic stir bar, a mixture of 4-ethynylbenzene (1.97 g, 16.86 mmol) and octanoyl chloride (3.02 g, 18.55 mmol) was dissolved in dichloromethane (60 mL). Afterwards, pyridine (2 g, 25.28 mmol) was added, and the reaction mixture was stirred overnight at room temperature. The reaction progress was monitored by TLC. After full conversion, the mixture was extracted with 1M HCl aqueous solution, 1M NaOH aqueous solution and brine. The organic solution was removed under reduced pressure.

Synthesis of octanoylamino-4-iodobenzene.
In a 100 mL round bottom flask equipped with a magnetic stir bar, a mixture of 4-iodoaniline (3.69 g, 16.86 mmol) and octanoyl chloride (3.02 g, 18.55 mmol) was dissolved in dichloromethane (60 mL). Afterwards, pyridine (2 g, 25.28 mmol) was added, and the reaction mixture was stirred overnight at room temperature. The reaction progress was monitored by TLC. After full conversion, the mixture was extracted with 1M HCl aqueous solution, 1M NaOH aqueous solution and brine. The organic solution was removed under reduced pressure.
The reaction progress was monitor by TLC. After full conversion was achieved, the reaction was quenched with water and neutralized by ammonia. After extraction with dichloromethane, the solvent was removed under reduced pressure. The crude product by column chromatography on silica gel, elution with petroleum ether/ dichloromethane. After evaporation, the resulting product was dried at 80 °C for 12 h to give 4,4'-(2,3,6,7-tetramethoxy-9,10-anthracenediyl) bis[benzaldehyde] as a lightyellow solid (1.57 g, 62%) and pure enough for the next step. 1